1. Field of the Invention
The present invention pertains to water-based compositions useful for forming acoustic- and vibration-damping coatings on substrates, particularly relatively thin, rigid materials such as sheet metal. In particular, the invention relates to compositions containing water, dispersed particles of one or more polymers, one or more particulate inorganic fillers, and expandable microspheres.
2. Discussion of the Related Art
To suppress the noise often created by the vibration of certain substrates such as those employed in the construction of vehicles, machines, marine craft, building materials and components, appliances, and the like, various aqueous vibration-damping coatings have been developed. Such coatings are recognized as having the advantages of being easy and relatively safe to handle and apply, since they generally do not contain large amounts of hazardous, volatile, or flammable organic solvents. However, the surface appearance of such coatings when applied to the substrate surface and dried or cured is often less than completely satisfactory. Very commonly, the coating surface is rough and uneven. Additionally, the damping characteristics of the water-based coatings are such that a relatively thick coating is required in order to suppress the noise and vibration to the desired extent. In addition to being less economical, the use of relatively thick coatings tends to further worsen the surface appearance problems typically encountered with such coatings.